He is preaching to the converted. He is lashing out at anyone who is not completely loyal. He is detaching himself from and delegitimising the institutions of American political life. And he is proclaiming conspiracies everywhere - in polls (rigged), in debate moderators (biased) and in the election itself (soon to be stolen).

In the presidential campaign's home stretch, Donald Trump is fully inhabiting his own echo chamber. The Republican nominee has turned inward, increasingly isolated from the country's mainstream and leaders of his own party, and determined to rouse his most fervent supporters with dire warnings that their populist movement could fall prey to dark and collusive forces.

This is a campaign right out of Breitbart, the incendiary conservative website run until recently by Stephen Bannon, now the Trump campaign's chief executive - and it is an act of retaliation.

The execution has been volatile. Since announcing last week that "the shackles have been taken off me," Trump, bolstered by allies on talk radio and social media, has been creating an alternate reality - one full of innuendo about Clinton, tirades about the unfair news media and prophecies of Trump's imminent triumph.A turbulent few weeks punctuated by allegations of sexual harassment have left Trump trailing Democratic nominee Hillary Clinton in nearly every swing state. Trump's gamble is that igniting his army of working-class whites could do more to put him in contention than any sort of broad, tempered appeal to undecided voters.

The candidate once omnipresent across the "mainstream media" these days largely limits his interviews to the safe harbour of Fox News, and most of them are with Sean Hannity, a Trump supporter and informal counsellor.

Many Republicans see the Trump campaign's latest incarnation as a mirror into the psyche of their party's restive base: pulsating with grievance and vitriol, unmoored from conservative orthodoxy, and deeply suspicious of the fast-changing culture and the consequences of globalisation.

"I think Trump is right: the shackles have been released, but they were the shackles of reality," said Mike Murphy, a veteran GOP strategist. "Trump has now shifted to a mode of complete egomaniacal self-indulgence. If he's going to go off with these merry alt-right pranksters and only talk to people who vote Republican no matter what, he's going to lose the election substantially."

Retired neurosurgeon Ben Carson, a Trump supporter and adviser, said the nominee's understanding of what motivates his base is "what got him through the primaries. The problem for him is that you have to expand that in order to win a general election. What's out there is powerful but not enough".

For Bannon and legions of Trump fans, Trump's approach is not only a relished escalation of his combativeness but also a chance to reshape the GOP in Trump's hardline nationalist image. "This is a hostile takeover," said former House Speaker Newt Gingrich, a Trump ally. "They believe the media is their mortal enemy and the country is in mortal danger, that Hillary Clinton would end America as we know it. This is not only about beating Hillary Clinton. It's about breaking the elite media which has become the phalanx of the establishment."

Trump's strategy was crystallized by his defiant speech on Friday in West Palm Beach, Florida, in which he brazenly argued that the women who have accused him of unwanted kissing and groping were complicit in a global conspiracy of political, business and media elites to slander him and extinguish his outsider campaign.

"This is not simply another four-year election. This is a crossroads in the history of our civilization that will determine whether or not we the people reclaim control over our government".

Trump said earlier last week: "The election of Hillary Clinton will lead to the destruction of our country. Believe me."